package com.sayalala.wework.wehook.utils;

import java.io.*;
import java.net.HttpURLConnection;
import java.net.URL;
import java.nio.MappedByteBuffer;
import java.nio.channels.FileChannel;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;


public class MD5Utils {
    /**
     * 默认的密码字符串组合，用来将字节转换成 16 进制表示的字符,apache校验下载的文件的正确性用的就是默认的这个组合
     */
    protected static char hexDigits[] = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f' };

    protected static MessageDigest messagedigest = null;
    static {
        try {
            messagedigest = MessageDigest.getInstance("MD5");
        } catch (NoSuchAlgorithmException nsaex) {
            System.err.println(MD5Utils.class.getName() + "初始化失败，MessageDigest不支持MD5Util。");
            nsaex.printStackTrace();
        }
    }

    /**
     * 生成字符串的md5校验值
     *
     * @param s
     * @return
     */
    public static String getMD5String(String s) {
        return getMD5String(s.getBytes());
    }

    /**
     * 判断字符串的md5校验码是否与一个已知的md5码相匹配
     *
     * @param password
     *            要校验的字符串
     * @param md5PwdStr
     *            已知的md5校验码
     * @return
     */
    public static boolean checkPassword(String password, String md5PwdStr) {
        String s = getMD5String(password);
        return s.equals(md5PwdStr);
    }

    /**
     * 生成文件的md5校验值
     *
     * @param file
     * @return
     * @throws IOException
     */
    public static String getFileMD5String(File file) throws IOException {
        InputStream fis;
        fis = new FileInputStream(file);
        byte[] buffer = new byte[1024];
        int numRead = 0;
        while ((numRead = fis.read(buffer)) > 0) {
            messagedigest.update(buffer, 0, numRead);
        }
        fis.close();
        return bufferToHex(messagedigest.digest());
    }

    /**
     * JDK1.4中不支持以MappedByteBuffer类型为参数update方法，并且网上有讨论要慎用MappedByteBuffer，
     * 原因是当使用 FileChannel.map 方法时，MappedByteBuffer 已经在系统内占用了一个句柄， 而使用
     * FileChannel.close 方法是无法释放这个句柄的，且FileChannel有没有提供类似 unmap 的方法，
     * 因此会出现无法删除文件的情况。
     *
     * 不推荐使用
     *
     * @param file
     * @return
     * @throws IOException
     */
    public static String getFileMD5String_old(File file) throws IOException {
        FileInputStream in = new FileInputStream(file);
        FileChannel ch = in.getChannel();
        MappedByteBuffer byteBuffer = ch.map(FileChannel.MapMode.READ_ONLY, 0, file.length());
        messagedigest.update(byteBuffer);
        in.close();
        return bufferToHex(messagedigest.digest());
    }

    public static String getMD5String(byte[] bytes) {
        messagedigest.update(bytes);
        return bufferToHex(messagedigest.digest());
    }

    private static String bufferToHex(byte bytes[]) {
        return bufferToHex(bytes, 0, bytes.length);
    }

    private static String bufferToHex(byte bytes[], int m, int n) {
        StringBuffer stringbuffer = new StringBuffer(2 * n);
        int k = m + n;
        for (int l = m; l < k; l++) {
            appendHexPair(bytes[l], stringbuffer);
        }
        return stringbuffer.toString();
    }

    private static void appendHexPair(byte bt, StringBuffer stringbuffer) {
        char c0 = hexDigits[(bt & 0xf0) >> 4];// 取字节中高 4 位的数字转换, >>>
        // 为逻辑右移，将符号位一起右移,此处未发现两种符号有何不同
        char c1 = hexDigits[bt & 0xf];// 取字节中低 4 位的数字转换
        stringbuffer.append(c0);
        stringbuffer.append(c1);
    }

    public static void main(String[] args) throws IOException {
        long begin = System.currentTimeMillis();

        File file = new File("D:/BaiduNetdiskDownload/01_SpringBoot全套视频教程2018年3月份录制2.0.x版本/01-SpringBoot简介.avi");
        if(!file.exists()){
            System.out.println("不存在");
        }
        String md5 = getFileMD5String(file);

          String md5_a = getMD5String("a");

        long end = System.currentTimeMillis();
        System.out.println("md5:" + md5 + " time:" + ((end - begin) / 1000) + "s");
        System.out.println(file.getPath());
    }

    public static String getNetFileMD5String(String imagePath) {
        try {
            // 创建URL
            URL url = new URL(imagePath);
            final byte[] by = new byte[1024];
            // 创建链接
            final HttpURLConnection conn = (HttpURLConnection) url.openConnection();
            conn.setRequestMethod("GET");
            conn.setConnectTimeout(5000);
            InputStream is = conn.getInputStream();
            File temp = File.createTempFile("temp", ".img");
            FileOutputStream outputStream = new FileOutputStream(temp);
            int len = -1;
            while ((len = is.read(by)) != -1) {
                outputStream.write(by, 0, len);
            }
            // 关闭流
            is.close();
            outputStream.close();
            String md5String = getFileMD5String(temp);
            temp.delete();
            return md5String;

        } catch (IOException e) {
            e.printStackTrace();
            return null;
        }
    }
}
